Method of manufacturing a turbine fan blade

ABSTRACT

A metal leading edge of a turbine fan blade is manufactured by cutting and shaping an elongated metal part. The metal part has front and rear edges extending lengthwise of the part, and has a generally wedge-shaped transverse cross-section with opposite sides diverging from the front edge toward the rear edge. A cavity is cut inward from the rear edge toward the front edge. This provides the part with a generally V-shaped transverse cross-section having opposite side walls diverging rearwardly from the front edge. A mandrel is inserted into the cavity, and the side walls of the V-shaped part are deflected toward each other to constrict the cavity into the configuration of the mandrel. The part is then mounted as a metal leading edge by inserting a turbine fan blade component into the constricted cavity and fastening the part to the component.

TECHNICAL FIELD

This technology relates to a fan blade for a turbine in an aircraftengine.

BACKGROUND

A jet engine for an aircraft has a turbine with fan blades that draw airinto the engine as the turbine rotates. The fan blades are exposed tothe atmosphere in front of the engine and have the potential for animpact with a bird or other foreign object that may be drawn into theengine. For this reason a turbine fan blade typically has a metalleading edge for structural reinforcement to protect the fan blade froma bird strike or the like.

SUMMARY

A metal leading edge of a turbine fan blade is manufactured by cuttingand shaping an elongated metal part. The metal part has front and rearedges extending lengthwise of the part, and has a generally wedge-shapedtransverse cross-section with opposite sides diverging from the frontedge toward the rear edge. A cavity is cut inward from the rear edgetoward the front edge. This provides the part with a generally V-shapedtransverse cross-section with opposite side walls diverging rearwardlyfrom the front edge. A mandrel is inserted into the cavity, and the sidewalls of the V-shaped part are deflected toward each other to constrictthe cavity into the configuration of the mandrel. The part is theninstalled as a metal leading edge by inserting a turbine fan bladecomponent into the constricted cavity and fastening the part to thecomponent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing parts of a turbine fan blade incross-section.

FIG. 2 is a schematic perspective view showing an initial condition of apart of the fan blade of FIG. 1.

FIG. 3 is a schematic sectional view showing an intermediate conditionof the part shown in FIG. 2.

FIG. 4 is a schematic view showing the part of FIG. 2 clamped to acutting fixture.

FIG. 5 is a schematic view illustrating a cutting step that places thepart in the intermediate condition of FIG. 3.

FIG. 6 is a schematic view illustrating a cutting and surface finishingstep.

FIG. 7 is a schematic view partially illustrating a shaping step.

FIG. 8 also is a schematic view partially illustrating the shaping step.

FIG. 9 is a schematic sectional view showing the part in a finishedcondition.

DETAILED DESCRIPTION

The apparatus shown in the drawings has parts that are examples of theelements recited in the claims. The following description thus includesexamples of how a person of ordinary skill in the art can make and usethe claimed invention. It is presented here to meet the statutoryrequirements of written description, enablement, and best mode withoutimposing limitations that are not recited in the claims.

As shown partially in FIG. 1, a turbine fan blade 10 has a body 12component formed of a composite material. A metal part 14 is mounted ona leading portion 16 of the body component 12 to define the leading edgeof the fan blade 10. Although the body component 12 is shownschematically as a single piece of composite material, it may compriseany suitable part or combination of parts that together provide the fanblade 10 with the overall configuration of an airfoil. The metal part14, which is preferably formed of titanium, provides the fan blade 10with structural reinforcement for protection against bird strikes.

The metal part 14 is initially formed as a forged metal strip having theelongated, generally rectangular configuration shown in FIG. 2. The part14 then has front and rear edges 20 and 22 extending lengthwise betweenits opposite ends 24 and 26. Although the part 14 will vary along itslength to conform with the airfoil configuration of the body component12 (FIG. 1), it maintains a generally wedge-shaped transversecross-section with opposite sides 30 and 32 diverging from the frontedge 20 toward the rear edge 22 as shown, for example, at the second end26 in FIG. 2.

In the illustrated example the opposite sides 30 and 32 have concavecontours, and the first side 30 is longer than the second side 32. Thefront edge 20 is a planar surface that is orthogonal to the oppositesides 30 and 32 at front corners 34 and 36 of the part 14. The rear edge22 has a non-planar contour extending between a rear corner 38 at thelonger side 30 and a rear corner 40 at shorter side 32. Importantly, theinitial thickness T1 of the part 14 at the rear edge 22 is substantiallygreater than the thickness T2 of the fan blade 10 (FIG. 1) where thefinished part 14 reaches over the leading portion 16 of the bodycomponent 12.

The metal part 14 of FIG. 2 obtains the configuration of FIG. 3 in amachining process. Specifically, the part 14 is clamped to a machiningfixture 50 as shown in FIG. 4, and is cut with a milling cutter 52 asshown in FIG. 5. The cutter 52, or one or more similar cutters ofdiffering sizes, cuts into the part 14 to form a cavity 55. The cavity55 extends lengthwise of the part 14 from end 24 to end 26, and extendstransversely inward from the rear edge 22 toward the front edge 20. Thisprovides the entire length of the part 14 with a generally V-shapedtransverse cross-section having opposite side walls 60 and 62 thatdiverge to the rear. Like the wedge-shaped cross-section of FIG. 2, theV-shaped cross-section of FIG. 3 will vary as needed for conformity withthe airfoil configuration of the body component 12. However, theoversized thickness T1 at the rear of the part 14 enables the cavity 55to have a correspondingly wide open end 65 along its full length.Additionally, the concave contours at the opposite sides 30 and 32enable the cutter 52 to provide the side walls 60 and 62 withcorrespondingly convex inner surfaces 66 and 68. The wide opening 65 andconvex inner surfaces 66 and 68 enhance the clearance through which thecutter 52 can be maneuvered within the cavity 55 as it advances inwardfrom the rear edge 22 toward the front edge 20.

In addition to the convex inner side surfaces 66 and 68, the cutter 52forms a concave inner surface 70 at the bottom of the cavity 55. Theinner surfaces 66, 68 and 70 are all provided with machined finishes.The part 14 is next transferred to a cutting mandrel 80 for machinefinishing at the exterior surfaces, as shown in FIG. 6. Cutting at theexterior also provides the part 14 with a newly formed front edge 82having a rounded contour suitable for the terminal leading edge of thefan blade 10 (FIG. 1).

A shaping step follows the cutting steps. As shown in FIG. 7, the part14 is placed on a shaping mandrel 90 such that a leading portion 92 ofthe mandrel 90 is received in the open cavity 55. The leading portion 92of the mandrel 90 has the same size and shape as the leading portion 16of the body 12 component upon which the metal part 14 is to be mountedas shown in FIG. 1. The part 14 and the mandrel 90 are heated to anelevated temperature and placed between a pair of heated forming dies 96and 98, as shown in FIG. 8. As the dies 96 and 98 are moved together,they deflect the side walls 60 and 62 of the part toward each other andinto overlying engagement with the leading portion 92 of the mandrel 90.This constricts the cavity 55 into the configuration of the leadingportion 92 of the mandrel 90 and, likewise, the leading portion 16 ofthe body component 12. Such shaping of the part 14 is preferablyaccomplished in a creep forming or warm forming process at an elevatedtemperature that is maintained below the forging temperature of thetitanium or other metal of which the part 14 is formed. The part 14 isthen removed from the forming dies 96 and 98 and the mandrel 90, and iscooled to room temperature. The cooled and shaped part 14, as shown inFIG. 9, is then mounted on the body component 12 without furtherheating, cutting or shaping, and is fastened to the body component 12 inany suitable manner known in the art.

The patentable scope of the invention is defined by the claims, and mayinclude other examples of how the invention can be made and used. Suchother examples, which may be available either before or after theapplication filing date, are intended to be within the scope of theclaims if they have elements that do not differ from the literallanguage of the claims, or if they have equivalent elements withinsubstantial differences from the literal language of the claims.

1. A method of manufacturing a metal leading edge of a turbine fan blade, comprising: providing an elongated metal part having a front edge extending lengthwise of the part, a rear edge extending lengthwise of the part, and a generally wedge-shaped transverse cross-section with opposite sides diverging from the front edge toward the rear edge; cutting a cavity inward from the rear edge toward the front edge to provide the part with a generally V-shaped transverse cross-section having opposite side walls diverging rearwardly; shaping the part by inserting a mandrel into the cavity and deflecting the side walls toward each other to constrict the cavity into the configuration of the mandrel; and mounting the part as a metal leading edge by inserting a turbine fan blade component into the constricted cavity and fastening the part to the component.
 2. A method as defined in claim 1 wherein the mounting step is performed without further shaping of the part after the cavity is constricted into the configuration of the mandrel.
 3. A method as defined in claim 1 wherein the opposite sides of the wedge-shaped cross-section have concave contours.
 4. A method as defined in claim 1 wherein the cutting step provides each side wall with a convex inner surface contour.
 5. A method as defined in claim 1 further comprising the step of providing exterior surfaces of the part with machined finishes prior to the shaping step.
 6. A method as defined in claim 1 further comprising the step of machining the part to provide a front edge with a rounded corner suitable as a terminal leading edge of the fan blade prior to the shaping step.
 7. A method of manufacturing a metal leading edge of a turbine fan blade, comprising: providing an elongated metal part having opposite ends, a front edge extending lengthwise of the part, a rear edge extending lengthwise of the part, and a generally wedge-shaped transverse cross-section with opposite sides diverging from the front edge toward the rear edge; cutting a cavity in the part extending lengthwise end to end and transversely inward from the rear edge toward the front edge to provide the entire length of the part with a generally V-shaped transverse cross-section having opposite side walls diverging rearwardly from the front edge; inserting a mandrel into the cavity; shaping the part by heating the part to an elevated temperature and deflecting the side walls of the heated part toward each other to constrict the cavity into the configuration of the mandrel; and mounting the part as a metal leading edge without further shaping at an elevated temperature by inserting a turbine fan blade component into the constricted cavity and fastening the part to the component.
 8. A method as defined in claim 7 wherein the cutting step provides each side wall with a convex inner surface contour.
 9. A method as defined in claim 7 further comprising the step of providing exterior surfaces of the part with machined finishes prior to the shaping step.
 10. A method as defined in claim 7 further comprising the step of machining the part to provide a front edge with a rounded corner suitable as a terminal leading edge of the fan blade prior to the shaping step.
 11. A method of manufacturing a metal leading edge of a turbine fan blade, comprising: providing an elongated metal part having a front edge extending lengthwise of the part and a rear edge extending lengthwise of the part; cutting a cavity inward from the rear edge toward the front edge to provide the part with a concave inner surface defining the bottom of the cavity and opposed inner side surfaces with convex contours reaching fully from the concave inner surface to the rear edge of the part; shaping the part by inserting a mandrel into the cavity and deflecting the opposed inner side surfaces toward each other to constrict the cavity into the configuration of the mandrel; and mounting the part as a metal leading edge by inserting a turbine fan blade component into the constricted cavity and fastening the part to the component.
 12. A method as defined in claim 11 wherein the mounting step is performed without further shaping of the part after the cavity is constricted into the configuration of the mandrel.
 13. A method as defined in claim 11 further comprising the step of providing exterior surfaces of the part with machined finishes prior to the shaping step.
 14. A method as defined in claim 11 further comprising the step of machining the part to provide a front edge with a rounded corner suitable as a terminal leading edge of the fan blade prior to the shaping step. 